Sheila Madrak , a San Diego-based wildlife biologist who specializes in sea turtles, has a simple answer. All turtles have two distinct features: A shell to which their ribs and vertebrae are fused, and a pelvic girdle that sits inside their rib cage. Turtles can be aquatic, semi-aquatic, or mostly terrestrial. Tortoises are turtles that live on land and aren't equipped for water. Or even underneath it, since some tortoises are burrowers, like the gopher tortoises of the southeastern United States.
Only sea turtles have true flippers. Most turtles have streamlined shells but there are some exceptions. Box turtles , for example, have a domed shell, as do Sonoran mud turtles and all tortoises. All turtles also have a gular scute , an extension of the lower shell that sticks out under the chin.
Gular scutes are more pronounced in males, who use them as weapons to flip an opponent over in a fight , Madrak says. For some extra complication, there are two suborders of turtle whose classifications are based entirely on how they move their necks.
They turn their heads to the side and hide them under the rim of their shells for protection. Sometimes misidentification could be fatal for the animal. In The Florida Fish and Wildlife Commission had three instances of people who had mistakenly released tortoise hatchlings into the ocean —where the land-dwelling creatures would likely drown.
If you find a turtle you think is in distress, call your state fish and wildlife commission or another professional who can identify the species and will know how to handle the circumstances. These reptiles did okay for millions of years without people, Madrak points out. All rights reserved. People are prone to stereotyping, but we love it when someone flips the script. They maintain a vegetarian diet, whereas many aquatic turtles are carnivorous or omnivorous.
And then there are the terrapins. These small Testudines are technically a species of turtle, and they live around brackish, swampy waters. And if you couldn't figure out if the photograph is a turtle, tortoise, or terrapin, here's the answer: it's a terrapin! Want to learn about a famously altruistic kind of tortoise? Click here to read about how gopher tortoises save their neighbors from forest fires. A Moment of Science is a daily audio podcast, public radio program and video series providing the scientific story behind some of life's most perplexing mysteries.
Learn More ». Give Now ». Noon Edition. Home Archives About Contact. By Rory Boothe Posted April 2, Most aquatic turtles, even those with harder, bony shells, have a more streamlined profile. Their shells are not as high as those of their land-bound brethren -- aquatics are much longer than they are tall. The most common land turtle in the pet trade is the box turtle. Not only is her shell taller than that of most aquatic turtles, but herplastron -- the belly-side of the shell -- is also partially movable at the front and back, as if it were hinged.
Unlike aquatic turtles that escape predators by fleeing into water, the box turtle doesn't swim well, but she can completely close herself up in her shell, protecting her legs, head and tail. Land turtles and aquatic turtles use their feet differently. Because aquatic turtles have to swim, most species have webbed claws. To tell whether you have an aquatic turtle, move its claws apart slightly. Aquatic turtles have a flap of skin between the claws that helps them swim more efficiently.
Often, their claws are also longer and sharper than those of land turtles, enabling them to grip muddy embankments and slippery stones when climbing out of the water. Land turtles lack both the webbing and sharp claws. Their claws are often dull from foraging for food , but dull claws make it easier to walk on dry land. Because they spend less time on land, aquatic turtles' legs are shorter than those of their land-dwelling cousins.
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